Abstract
There is a significant interest in the computational physics community to perform lattice quantum chromodynamics (LQCD) simulations, which can run into the trillions of operations. LQCD computations solve a sparse linear system using a Wilson Dslash kernel, which has an arithmetic intensity of 0.88–2.29. This makes Dslash memory bandwidth-bound on most architectures, including Intel Xeon Phi Knights Corner (KNC). Most research optimizing the Dslash operator has been focused on single right-hand side (SRHS) linear solvers. There is a class of LQCD computations which aims to solve systems with multiple right-hand sides (MRHS), presenting additional opportunities for data reuse and vectorization. We present two approaches to MRHS Dslash: a vector register blocking approach and one using the software package QPhiX with a custom code generator for low-level intrinsics. We observed significant speedups using our approaches, with sustained performance of over 700 GFLOPS (single precision) in one instance. We achieved up to 29 % of theoretical peak performance compared to a maximum of 13 % obtained by the previous SRHS method using QPhiX.
Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.
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Acknowledgments
This work was partially supported by a grant from Jefferson Lab. Aaron Walden and Sabbir Khan were also partially supported by the Old Dominion University Modeling and Simulation Fellowship Program and gratefully acknowledge this support. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
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Walden, A., Khan, S., Joó, B., Ranjan, D., Zubair, M. (2016). Optimizing a Multiple Right-Hand Side Dslash Kernel for Intel Knights Corner. In: Taufer, M., Mohr, B., Kunkel, J. (eds) High Performance Computing. ISC High Performance 2016. Lecture Notes in Computer Science(), vol 9945. Springer, Cham. https://doi.org/10.1007/978-3-319-46079-6_28
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